Methods of recycling and/or upgrading olefin (co)polymers

ABSTRACT

The present invention relates to a method of recycling and/or upgrading an olefin (co)polymer, olefin (co)polymer scrap and/or mixtures thereof including adding effective amounts of a vinyl silane and a free radical initiator to graft the vinyl silane to the olefin (co)polymer. The present invention also relates to olefin (co)polymers, olefin (co)polymer scrap and/or mixtures thereof whenever recycled and/or upgraded by the method defined above and articles which are composed wholly or partly of them.

The present invention relates to methods of recycling and/or upgradingolefin (co)polymers, especially olefin (co)polymer scrap. The methodshave particular application to polyethylene or its scrap, morespecifically high density polyethylene (HDPE) used in milk bottles.

Considerable amounts of milk bottle scrap are recovered, but there havebeen insufficient economically useful applications developed to use therecovered product. The use of milk bottle scrap as a raw material tomanufacture articles of higher added value such as bottles, containersfor motor oils or chemicals, pipes and tubes is currently not possible.

Milk bottles are composed of high density polyethylene (HDPE), of gradeswhich are designed for one processing step only. The recycling of milkbottle material has either not been possible or has caused considerableproblems. Such problems include stress cracking, too many pinholes andnon-uniform wall thickness, together with the negative public opinionassociated with the use of recycled materials in food applications.

The environmental stress crack resistance (ESCR) of milk bottle materialand its scrap as defined in ASTM No. D1693B, is very low. As aconsequence, the ESCR of the recovered material is unacceptable in mostapplications.

Attempts have been made to use recovered milk bottle scrap inapplications such as pipes, films and mobile garbage bins. However, theproportion of scrap that could be incorporated without seriousdeterioration in properties was uneconomically low. The low ESCR wasparticularly problematic.

A requirement accordingly exists for methods of recycling and/orupgrading (co)polymer scrap, in particular milk bottle scrap so that itcan be used in higher value-added applications.

According to the present invention there is provided a method ofrecycling and/or upgrading an olefin (co)polymer, olefin (co)polymerscrap and/or mixtures thereof including adding effective amounts of avinyl silane and a free radical initiator to graft the vinyl silane tothe olefin (co)polymer.

Further according to the present invention there is provided a method ofupgrading an olefin (co)polymer, olefin (co)polymer scrap and/ormixtures thereof which fails the ESCR test as defined in ASTM No. D1693Bincluding adding effective amounts of a vinyl silane and a free radicalinitiator to graft the vinyl silane to the olefin (co)polymer.

The present invention also provides an olefin (co)polymer, olefin(co)polymer scrap and/or mixtures thereof whenever recycled and/orupgraded by the methods defined above.

The present invention further provides articles which are composedwholly or partly of the olefin (co)polymer, olefin (co)polymer scrapand/or mixtures thereof whenever recycled and/or upgraded by the methodsdefined above.

The term “scrap” is used herein in its broadest sense and refers todiscarded or waste (co)polymers which need to be recycled, reprocessedand/or upgraded. It is preferable to use the method of the presentinvention for recycling and/or upgrading (co)polymer scrap for reasonsof economy and cost.

Suitable olefin (co)polymers and their scrap include ethylene(co)polymers such as polyethylene, ethylene-propylene copolymers,ethylene-propylene-diene terpolymers (EPDM), ethylene vinyl acetatecopolymers (EVA), copolymers of ethylene-alkyl acrylates, for exampleethylene-ethyl acrylate (EEA) and ethylene-butyl acrylate (EBA) andtheir terpolymers with maleic anhydride or mixtures thereof. Thepreferred olefin (co)polymer is polyethylene of all grades and typesincluding high-density polyethylene (HDPE), medium density polyethylene(MDPE), low density polyethylene (LDPE), very low density polyethylene(VLDPE), ultra low density polyethylene (ULDPE) and linear low densitypolyethylene (LLDPE). It will be appreciated that the above olefin(co)polymers are also available as metallocene catalyst (co)polymers.Preferably the (co)polymers have a specific gravity (S.G.) of aboveabout 0.936. HDPE or its scrap is particularly preferred as this is thepolymer from which many plastic bottles, in particular milk bottles aremanufactured. More preferably, the HDPE has a S.G above about 0.942,even more preferably above about 0.945 and most preferably about 0.95 toabout 0.96.

While both homopolymers and copolymers can be used in the method of thepresent invention, preferably homopolymers are used. It will beappreciated that the homopolymer may contain up to about 5% by weight ofcomonomer.

In a particularly preferred embodiment, the (co)polymer is (co)polymerscrap or mixtures of (co)polymer scrap and (co)polymer.

Prior to the grafting step, the (co)polymer is preferably collected,sorted, washed, granulated, pelletised and/or filtered. The (co)polymeror part thereof may also be grinded and/or milled into powder form andused as such or a portion of it mixed with granules.

The (co)polymer which may be in the form of granules, pellets, powderand/or dices can then be pre-dried for example in warm air, hot air ordesiccated air to low residual moisture levels, preferably less thanabout 500 ppm, more preferably less than about 200 ppm. The (co)polymermay then be mixed in any suitable known apparatus, such as, for example,a continuous mixer or extruder, internal mixer, discontinuous mixer suchas Banbury type mixers or batch mixers. Continuous mixers or extrudersare preferred. Combined mixers with a first part having two mixingcylinders similar to those of an internal mixer and a second part havingan extruder of the single or twin screw type, for example, theFarrel-Pomini type can also be used. Most preferred are twin screw,co-rotating extruders or mixers or compounding machines.

The continuous mixer may be either a twin-screw mixer with counterrotating or preferably co-rotating screws which have mixing sections onthem, for example, a ZSK mixer from Werner and Pfleiderer, a twin screwmixer from Reifenhauser or a Buss-ko-kneader or single screw extruderwith sufficient mixing ability in the barrel or cylinder of theextruder.

The (co)polymers and/or additives can be added or fed into differentports of the mixing apparatus, for example, in the first third, secondthird or final third of the length of the co-extruder or twin-screwmixer.

The length of the mixing apparatus for mixing, melting and grafting canbe from about 7:1 (length:diameter) to about 40:1, preferably about 10:1to about 36:1, most preferably about 22:1 to about 36:1 depending on thetype of mixing apparatus, types of materials used, productivity andcosts. A higher ratio from 22:1 to 40:1 is preferred as there is ahigher residence time for the mixing, melting and grafting which,assuming the same residence or reaction time for the grafting, means ahigher output. The grafting time and thereby the output is alsodependent on the type of (co)polymer(s) to be grafted and the type ofvinyl silane and initiator mix, in particular the half life time ordecomposition time of the initiator at the grafting temperature.

The vinyl silane may be a vinyl alkoxy silane such asvinyl-tris-methoxy-silane (VTMOS), vinyl-tris-methoxy-ethoxy-silane,vinyl-tris-ethoxy-silane, vinyl-methyl-dimethoxy-silane andgama-methacryl-oxypropyl-tris-methoxy-silane.

The term “free radical initiator” is used herein in its broadest senseand refers to an unstable molecule or compound which generates freeradicals. More specifically, the free radicals are generated when theinitiator is heated to temperatures of above the melting point of the(co)polymer(s), their scrap and the initiator or in general to melt atprocessing temperature. Examples of suitable initiators includeperoxides such as dicumyl peroxide (DCP, Dicup), di-tertiary-butylperoxide (DTBP), di-tertiary-butylcumyl peroxide (DTBCP),di(tert-butylperoxy-isopropyl)benzene (Luperox F),2,5-dimethyl-2,5-di(tert.butylperoxy)hexane (Luperox 101), and otherknown dialkylperoxides and diarylperoxides. The free radical initiatoris preferably added in an amount of about 0.05% to about 0.3% by weightof the (co)polymer, more preferably about 0.08% to about 0.2% by weight,most preferably about 0.10% to about 0.16% by weight. It will beunderstood that, by having a defined ratio of initiator to vinyl silane,for example about 1:10 to about 1:15 which will depend on the type ofvinyl silane, the type of initiator and their active components ormolecular weights, the amount of initiator will vary in correlation withthe amount of vinyl silane added.

The vinyl silane is preferably mixed with the free radical initiator andthis mix may be added in an amount from about 0.5 to about 2.4% byweight of the (co)polymer, preferably about 0.8 to about 2% by weight,more preferably about 0.9 to about 1.6%, even more preferably 0.9% to1.4%, most preferably about 1% to 1.2%.

Alternatively, the vinyl silane and initiator mix can be incorporated,adsorbed to and/or absorbed into a carrier, such as, for example, otherpolyolefins advantageously in the form of granules or particles andadded to the (co)polymer for grafting.

The vinyl silane may also be added separately to the free radicalinitiator and in this case the above amounts will be reduced by theamount of initiator contained in the mix, such as about 0.1 to about0.2% by weight of the (co)polymer, usually about 0.1% to about 0.15%.

The vinyl silane and the initiator can also be added separately, in apre-mixing step, to the polyolefin (co)polymer and/or scrap. Preferablysome powder is added, more preferably HDPE powder is added in an amountof about 5 to about 10% or more of the (co)polymer mix, to which theinitiator and the silane is then added and the mix is then fed into themixing apparatus whereby the whole of the (co)polymer and scrap can be apowder.

It will be understood that the amount of vinyl silane added togetherwith the initiator or the amount of silane per se will depend on thetype of (co)polymer being recycled and/or upgraded, the type of thevinyl silane, the type of initiator added and on the desired degree ofcross-linking or of other related properties such as ESCR or resistanceto chemicals.

Preferably, the grafting step is performed at a melt temperature of fromabout 180° C. to about 230° C., more preferably about 190° C. to about220° C., most preferably about 200° C. to about 220° C. Alternatively, amelt may be formed of the (co)polymer prior to adding the vinyl silaneand initiator in the (co)polymer or (co)polymer melt for grafting.

In another embodiment, one or more additives and/or fillers known in theart of polymer processing can be added either before, during or aftergrafting of the vinyl silane. It will be appreciated that such additivesand/or fillers can also be included in the pre-mixture of the silane andinitiator.

Suitable additives include antioxidants, processing and/or thermalstabilisers, for example, tris (2,4-ditert-butylphenyl) phosphite(phosphite based), pentaerythritol tetrakis(3-(3,5-di-tertbutyl-4-hydroxyphenyl)propionate),octadecyl-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,3,3′,3′,5,5′,5′-hexa-tert-butyl-a,a′,a′-(mesitylene-2,4,6-triyl)tri-p-cresol(phenolic based) and dioctadecyl-3,3′-thiodipropionate (thioesterbased); metal deactivators and/or copper inhibitors, for example,oxalyl-bis(benzylidenehydrazide and2,3-bis((3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl))propionohydrazide;UV stabilisers, for example,poly((6-((1,1,3,3-tetramethylbutyl)amino)-1,3,5-triazine-2,4-diyl)((2,2,6,6-tetramethyl-4-piperidinyl)imino)-1,6-hexanediyl((2,2,6,6-tetramethyl-4-piperidinyl)imino))),bis(2,2,6,6-tetramethyl-4-piperidyl)sebaceateandphenol-2-(5-chloro-2H-benzotriazole-2-yl)-6-(1,1-dimethylethyl)-4-methyl;blowing agents which may be either endothermic or exothermic forexample, p.p-oxybis benzene-sulfonyl-hydrazide, azo-iso-butyro-nitrileand azodicarbonamide; catalysts, for example, cross-linking catalystssuch as dibutyltindilaurate and dioctyltindilaurate; and pigments, forexample, inorganic pigments such as titanium dioxide and carbon blackand organic pigments. The pigments can also be added as a colourmasterbatch or concentrate.

Suitable fillers include mineral fillers such as calcium carbonate,magnesium calcium carbonate, hydrated basic magnesium carbonate, talc,clays which may be calcined, kaolin, aluminium hydroxide (aluminiumtrihydrate) and magnesium hydroxide. The fillers may be optionallycoated with, for example, stearates such as calcium stearate, magnesiumstearate or stearic acid or silanes such as vinyl silanes. Some of thesefillers have flame retardant properties, as do some of the (co)polymersdefined herein. However, if desired other flame retardants may be addedsuch as halogenated flame retardants based on brominated and/orchlorinated materials; phosphate based compounds, for example, ammoniumpolyphosphate; and esters of phosphoric acid. The fillers preferablyhave a low moisture/humidity level of less than about 1000 ppm, morepreferably less than about 500 ppm, most preferably less than about 200ppm.

The non-halogenated flame retardants may be added in one step ifsufficiently dry or preferably in a separate step after the grafting ofthe vinyl silane onto the (co)polymer so as to avoid interference withor influence on the grafting of the vinyl silane by the initiator. Inthe presence of acidic by-products such as hydrochloric or hydrobromicacid from the halogenated compounds generated at higher processingtemperatures, the initiator decomposition which is normally a radicaldecomposition process needs to initiate the grafting of the silane, maybe changed from a radical mechanism and diverted to an ionic mechanismwith ionic side products which reduce the grafting of the silane ontothe (co)polymer.

The type, combination and amount of additives and/or fillers may bechosen according to the intended final application. Additives generallyare added up to about 10% and fillers up to about 50% by weight based onthe amount and type of (co)polymer and/or scrap being recycled and/orupgraded.

Either before, during or after the grafting step, other (co)polymers ortheir scrap can be added to enhance the properties of the recycledand/or upgraded (co)polymer. Examples of such (co)polymers includepolyolefins such as ethylene vinyl acetate copolymer (EVA), ethyleneethyl acrylate copolymer (EEA), ethylene butyl acrylate copolymer (EBA),ethylene propylene rubber (EPR), ethylene-propylene copolymer (EPM),ethylene propylene-diene terpolymer (EPDM), ethylene-butylene copolymer(EBM), ethylene butylene-diene terpolymer (EBDM), very low densitypolyethylene (VLDPE), ultra low density polyethylene (ULDPE) linear lowdensity polyethylene (LLDPE), low density polyethylene (LDPE) and mediumdensity polyethylene (MDPE). Examples of (co)polymers which can be addedafter the grafting step possibly in another processing step includepolypropylene, nitrile butadiene rubber, chlorinated polyethylene andchloro-sulfonated polyethylene. The other (co)polymers may be added inamounts of from about 5% to 95% of the recycled and/or upgraded(co)polymer, preferably about 5% to about 50%. The other (co)polymersmay be used in their original form or be upgraded, recycled and/orgrafted with silanes. The amount of other (co)polymers added will dependon whether the intention is to modify the grafted (co)polymer or to usethe grafted (co)polymer to modify other polymers.

The final recycled and/or upgraded polymer is preferably melted, mixedand then filtered and/or screened, for example, using a filter or screenpack in order to remove any contamination or foreign matter particleseither during or as a separate step to the method of the invention. Thefinal (co)polymer can optionally then be pelletised either by die-facecutting or by extruding strands which are cooled, for example, in awater bath and then cut into granules. Tapes may also be formed orextruded with the more elastic compounds which are then diced later, forexample, using a Condux dicer or pelletiser. The granules or pellets maythen be dried by known methods, such as, in warm air and preferablydesiccated air, to a level of preferably less than about 500 ppm, morepreferably less than about 200 ppm packed into suitable vessels such asbags, boxes or containers, preferably with a metallic layer or ametallic film to avoid diffusion or penetration of water vapour.

The recycled and/or upgraded (co)polymer of the invention can be formedby any suitable known process including injection moulding, blowmoulding, compression moulding, extrusion calendering or other knownconversion processes into articles such as bottles, containers, boxes,tubes, pipes, cables, profiles, sheets, films and pre-forms.

Suitable catalysts for cross-linking include di-butyl tin dilaurate(DBTDL), di-octyl tin dilaurate (DOTDL) or other known catalysts whichare used for crosslinking or curing the compounds at temperatures fromambient to elevated temperatures up to about 115° C. in the presence ofwater, steam, moisture or humid air.

When a cross-linking catalyst is used in a one step process, it is addedto the (co)polymer preferably as a mix with the vinyl silane andinitiator either before or during the grafting step or just after thegrafting step, but in the same apparatus or process step, the recycledand/or upgraded (co)polymer is formed after leaving the apparatus intothe desired article.

In a two step process, the catalyst is added in the second step whichcomprises mixing and melting the grafted (co)polymers and the catalystmasterbatch and the subsequent forming process which is conducted in asuitable forming apparatus, such as, for example, an extruder, injectionor blow moulding machine or calender.

In another variation, no catalyst is added in the two steps of graftingand forming and the grafted and formed material cross-links naturally inthe presence of humidity or without a catalyst but over a longer timeperiod. Alternatively, the catalyst may be added as a solution ordispersion in water into the (warm or hot) water bath in which theformed products may be cross-linked or cured.

Alternatively, the final (co)polymer or articles manufactured therefrommay be cross-linked in the presence of water, water vapour or steam attemperatures from about ambient up to about 115° C., preferably about70° C. to about 100° C., at ambient pressure more preferably from about80° C. to about 95° C. at ambient pressure. Preferred ranges forcross-linkable HDPE are from about ambient to about 115° C., preferablyabout 90° C. to about 100° C. and for cross-linkable LLDPE are fromabout ambient to about 105° C., preferably about 90° C. to about 100° C.Cross-linking times range from about 2 hours to about 60 hours or moredependent on the temperature and the thickness of the product or severaldays to weeks at ambient temperature.

The degree of cross-linking can be tested using any suitable knowntechnique such as the solvent extraction test or gel test, where theinsoluble, cross-linked fraction in new materials has to achieve aminimum, which is preferably about 50% in new materials but which may behigher or lower for recycled and/or scrap materials, depending on thearticle and type of (co)polymer recycled and/or upgraded and theultimate use. The degree of cross-linking can also be tested by usingthe hot set test as described by Australian Standard AS-1660 andequivalent International standards: IEC, BS, VDE/DIN, where dumbbells ofthe material with weights attached are placed in a hot air oven at 200°C. and the elongation is measured after 15 minutes with the weightsattached and later with the weights removed.

For some applications, the degree of cross-linking can be tested usingthe hot-set test at 150° C. in an air oven. The quoted minimum in thegel test and/or maximum elongation in the hot set test are applicable tothe grafted (co)polymer recycled and/or upgraded mainly based onpolyethylene such as HDPE. Different results will be obtained when other(co)polymers, additives and/or fillers are added.

The recycled and/or upgraded (co)polymer can also be used to improveproperties of other polymeric material, for example, about 5% to about95% of grafted cross linkable polyethylene can be added to improve theESCR and/or thermo-mechanic properties of other materials. Preferablythe recycled and/or upgraded (co)polymer may be added in proportions ofabove about 30%, preferably above about 50%.

Conversely it is preferable to use more than about 50% of the recycledand/or upgraded (co)polymer, more preferably above about 70%, even morepreferably above about 85%, most preferably above about 90% or up to100% of the polymer for economical reasons.

The invention will now be described with reference to the followingexamples. These examples are not to be construed as limiting theinvention in any way.

In the examples, a mixture of vinyl tris-methoxysilane (VTMOS) andperoxide, (trade name “SILOX” VS911) was used to graft the HDPE bottlescrap, original HDPE, EVA and/or a metallocene polyolefin (AffinityEG8200) in the form of granules or pellets with some powder added forprocessing. The bottle scrap used was either used as such dry orpre-dried for 24 hours with hot dehumidified air in a dehumidifier. Inexamples 1 to 7, 9 and 12 to 18, the SILOX and the HDPE bottle scrap wasadded just after the hopper of the co-extruder into a port of theco-extruder. In examples 8, 10 and 11 the SILOX, part of the HDPE bottlescrap and HDPE powder were mixed together in a high speed mixer at 150rpm for 1 minute and then at 300-350 rpm for another minute. This mixwas then added to the HDPE prior to the mixing/grafting.

The method of examples 8, 10 and 11 is preferred. We found that thegrafting reaction was better, the silane was grafted more completely andno odour of unreacted silane was felt on the outcoming hot granules,whereas when the SILOX was added into the melt there was some odourdetected.

The examples were run on a co-rotating twin screw extruder, Werner &pfleiderer ZSK type, L:D ratio 36:1 (36D), 53 mm screw diameter.Examples were (also) run on a Toshiba TEM 120 mm co-rotating twin screwextruder continuous mixer, L:D ratio 36:1, screw diameter 120 mm.

The screw rotations per minute (rpm's) were in the available range up to300 rpm, preferably 200 rpm. The cylinder temperatures were in thelimits of between 180-240° C., preferably around 200-220° C. The melttemperatures were between the limits of 180-240° C., but generallybetween 200-220° C. depending of which material(s) (co)polymer(s) wereused for grafting.

After mixing and grafting in the twin screw extruder, strands with around cross-section were extruded, cooled in a water bath, granulated,dried and packed.

For longer storage, samples were packed in either plastic bags or bagswith laminated aluminium foil or in plastic or glass bottles.

The samples were then kept for later reference and cross-checking of themelt flow index (MFI) (which in some cases tends to reduce in time). Insome cases, a processing aid masterbatch containing about 5%fluorocarbon polymer was added in an amount of 1%.

The samples of grafted, cross-linkable granules were then furtherprocessed usually by adding DOTDL catalyst masterbatch (made in housefrom DOTDL and HDPE) in a proportion of 5:95 to the main grafted(co)polymer and/or scrap i.e. about 1:20 or about 5%, were then furtherprocessed in a laboratory extruder making tapes and/or an injectionmoulding machine for making plaques from which dumbells were cut and orin a film blowing extrusion.

The samples cut from the tapes or dumbells were made by injectionmoulding and then cross-linked at temperatures between ambient, RT (roomtemperature) however for testing of crosslinking they were mainlycrosslinked in steam at between 90 and 100° C., at atmospheric pressure,or to further accelerate the process of preparation and testing, at upto 115° C. in a pressure cooker.

The times used in the laboratory were 30 minutes, 1 hour, 2 hours or 4hours. 30 minutes and 1 hour were used to expedite testing obtaininggood cross-linking, however 4 hours was used later to obtain an optimalcross-linking. In fact examples 6, 9, 10 and 11 were cross-linked for 4hours at 115° C., with 1.2% Silox added and showed excellentcross-linking, e.g. HST hot set test results at 200° C. under load hadvery excellent elongations of only around 16% and/or up to around 33%.The AS and International Standards allow up to 175% elongation underload. A good quality silane cross-linking is from 60% up to around 100%or 120%. Excellent cross-linking is when the HST is about 10 to 60%elongation. Without the load the elongation was around 0%, the standardallows max. 15%. This shows potential to further reduce the amount ofsilane, as seen later. Different results apply when elastomer is addedto the main polyethylene or scrap.

Further tests were carried out as follows:

-   -   mechanical properties (tensile strength (TS) and elongation at        break (EB)),    -   oil resistance (OR) test (ASTM oil number 2, as in ASTM,        AS 1660) 4 hours at 70° C. (as for plasticised PVC, e.g. for        cables, which has a moderate resistance to oil), 18 hours at        100° C. and 18 hours at 120° C. (as for oil resistant rubbers).        (LDPE or regular XLPE based on LDPE are not known to be oil        resistant). The retention in % of mechanical properties after        oil immersion, indicates the oil resistance. This depends of the        type of oil or solvent, chemical used.    -   ESCR=Environmental Stress Crack Resistance (ASTM 1693B) The test        was carried out to ASTM on dumbells at 50° C. in a solution of        detergent in water. This test shows resistance to detergents,        surfactants, soaps and is an indication of resistance to stress        crack in the environment & in chemicals, etc. Injection moulded        dumbells, (unnotched dumbells) were used. The ESCR improved        considerably, from not resistant i.e. a few hours to 48 hours        (requested by some standards for cables) to 1000 hours and more.        Some samples reached up to 5000 hours and are continuing into        7000 hours, depending on criteria such as time to failure of 20%        of the samples (F20), or F50 (time to failure of 50% of the        samples). F0 means that there are no failures.

Except where shown otherwise in the examples antioxidant IRGANOX 1330and metal deactivator Naugard XL-1 (Uniroyal) were added separately tostabilise the HDPE, in a masterbatch together with the DOTDL catalystwhich was added to accelerate crosslinking, after grafting during thepreparation of test samples by extrusion and/or moulding.

The masterbatch was composed of Irganox 1330 4.5%, Naugard XL-11.5%,Catalyst Metatin 812ES 0.4% in HDPE GM5010 (powder) 93.6% compounded andgranulated. 5% of this masterbatch was added to 95% of the HDPE.

In other examples the antioxidant and metal deactivators are shown. Inthese examples, the same amount of DOTDL catalyst was added in the sameproportions as a masterbatch separately, prior to the extrusion ormoulding of the samples, to accelerate cross-linking.

In regular use, part of the antioxidants, and particularly processstabilisers e.g. Irgafos 168 process stabilisers are added at thecompounding and grafting stage and another part are added together withi.e. in the catalyst masterbatch.

Cross-linking of the samples was in hot water and/or steam (watervapour). The amounts quoted in the examples are in weight part per 100parts of base (co)polymer to be recycled and/or upgraded.

The quantities are shown in phr (parts per hundred parts weight of HDPE,bottle grade).

In some cases where materials from previous examples are used and mixedwith other materials, % by weight are shown. “HDPE bottle scrap” refersto “milk bottle scrap” in the examples.

ESCR is conducted at 50° C. in a solution of 10% detergent in water. F0means no failure, F10 means one failure of 10 dumbells, F20 is Failureof 2 dumbells and F50 is failure of 5 dumbells out of 10.

EXAMPLE 1

HDPE, bottle scrap granulated 100 Vinyl silane and peroxide mix (SiloxVS911) 1 phr Antioxidant and catalyst MB (masterbatch) 5 phr (addedlater, prior to forming and cross-linking) Hot Set Test (HST) 200° C.,under load, (HST): 70%

EXAMPLE 2

HDPE, bottle scrap granulated 100 Vinyl silane and peroxide mix (SiloxVS911) 1.2 phr Antioxidant and catalyst MB (added later)   5 phr HST 50%

EXAMPLE 3

HDPE, bottle scrap, granulated and pre-dried 100 Vinyl silane andperoxide mix (Silox VS911) 1 phr Antioxidant and catalyst MB (addedlater) 5 phr HST 40%

EXAMPLE 4

HDPE, bottle scrap granulated and pre-dried 100 Vinyl silane andperoxide mix (Silox VS911) 1.2 phr Antioxidant and catalyst MB (addedlater) 5 phr HST 43% ESCR F0 (stopped test at) 3800 hrs+ TensileStrength (TS) 24.3 Mpa Elongation at Break (EB) 226% Oil Resistance(ASTM Oil #2)to AS 18 hrs at 120° C., % Retention of: TS 74% EB 69%ESCR, HST and OR are excellent in this example.

EXAMPLE 5

HDPE HD6095*, (S.G. 0.960, MFI = 0.8) 100 *Original bottle grade polymerVinyl silane and peroxide mix (Silox VS911) 1.2 phr Antioxidant andcatalyst MB (added later) 5 phr HST 17% ESCR 3000 hrs+

EXAMPLE 6

HDPE HD6095, (S.G. 0,960, MFI = 0.8) 100 Vinyl silane and peroxide mix(Silox VS911) 1.4 phr Antioxidant and catalyst MB (added later) 5 phrHST 10% ESCR F0 3800 hrs+

EXAMPLE 7

HDPE, scrap, melt filtered and pelletised 100 Vinyl silane and peroxidemix (Silox VS911) 1.2 phr Antioxidant and catalyst MB (added later) 5phr HST 37% TS 22.3 Mpa EB 251% O.R. (120° C., 18 hrs), ret. of TS 63%O.R. (120° C., 18 hrs), ret. of EB 77%

EXAMPLE 8

HDPE milk bottle scrap, granulated and pre-dried 87.68% HDPE GF7660powder (Qenos)   10% Vinyl silane and peroxide mix (Silox VS911)  1.2%Irgafos 168  0.1% Process aid masterbatch    1% Calcium Stearate  0.02%Catalyst masterbatch (DOTDL based)    5% added later, prior to forming(5% to 95% of the above) HST   33% ESCR F30 at 96 hrs Not reached F40 at302 hrs 302 hrs++ TS 26 MPa EB   140% O.R. (120° C., 18 hrs), retentionof TS   60% O.R. (120° C., 18 hrs), retention of EB   151%*(*denotes that the EB has increased by 51%)

EXAMPLE 9

Grafted HDPE bottle scrap from Example 4 50% (100 phr) HD6095 originalbottle grade(thermoplastic) 47.5% (95 phr) Antioxidant and catalystmasterbatch 2.5% (5 phr) HST 47% TS 22 Mpa EB 175%

EXAMPLE 10

HDPE milk bottle scrap, granulated and pre-dried 64.48% (100 phr) GF7660 (HDPE) powder 10% (15.5 phr) EVA (45%) Levapren450 (co-polymer),Bayer 23% (30.9 phr) Vinyl silane and peroxide mix (Silox VS911) 1.4%Irgafos 168 0.1% Process aid masterbatch 1% Calcium stearate 0.02%Catalyst masterbatch, (DOTDL based) 5% added later, prior to forming,(5% to 95% of the above) HST 17% ESCR F0 302 hrs TS 14 MPa O.R. (120°C.) retention of TS 70% ESCR F0 (started recently), F0 302 hrs++(*has potential to last longer at F0)

EXAMPLE 11

Pre-Mix of: Granulated bottle scrap (HDPE), pre-dried  73.8% Levapren450 (EVA copolymer)  26.2% This pre-mix was then further compounded:Pre-mixed EVA and bottle scrap (from above) 87.78% GF7660 powder (HDPE)(Qenos)   10% Vinyl silane and peroxide mix (Silox VS911)  1.4% Irgafos168  0.1% Process aid masterbatch    1% Catalyst masterbatch(DOTDLbased)    5% (added later, prior to forming 5% to 95% of the above) HST  33% ESCR (started recently) F0 302 hrs++ TS 13 O.R. (100° C., 18 hrs),retention   70% TS (100° C., 18 hrs), retention   77% TS (100° C., 18hrs), retention   114%

EXAMPLE 12

HDPE, bottle scrap, granulated and pre-dried 100 Calcium carbonatemasterbatch  18 phr (Omyacarb 2T 80%, LLDPE 20%) Vinyl silane andperoxide mix (Silox VS911) 1.4 phr Antioxidant and catalyst (DOTDL)masterbatch   5 phr (added later, prior to forming) HST  30% TS 22 MPaEB 105% Excellent HST was obtained in the presence of CaCO₃ filler.

EXAMPLE 13

Grafted HDPE bottle scrap from example 1 100 (50%) HD6095 (milk bottlebase resin) (Qenos) 100 phr (50%) Antioxidant and catalyst masterbatch *% (added later, prior to forming, . . . % to . . . % of the above) HST 57% ESCR F90 at 23 hrs TS 22.7 Mpa EB 267% O.R. retained, TS  63% ″ 65%

EXAMPLE 14

Grafted HDPE bottle scrap from Example 4   75% (100 phr) HD6095 21.25%(28.3 phr) Catalyst and antioxidant masterbatch  3.75% (4.9 phr) (addedlater, prior to forming) HST   23% ESCR F0 7016 hrs+

EXAMPLE 15

HDPE bottle scrap grafted from Example 4   50% (100 parts) but 1.4%Silox VS911 HD6095 (HDPE bottle grade base resin) 47.5% (95 phr) andadded later, separately, prior to forming: Catalyst and antioxidantmasterbatch  2.5% (5 phr) HST   37% ESCR F50 1500 hrs TS 22.7 Mpa EB 115% O.R. (18 hrs, 200° C.), ret. TS   70% EB  136%

EXAMPLE 16

Grafted HDPE bottle scrap from Example 7   75% (100 parts) HD6095 (HDPEbase resin, bottle grade) 21.25% (28.3 phr) Catalyst and antioxidantmasterbatch  3.75% (5 phr) (added later, prior to forming) HST   17%ESCR reached F20 at 358 hrs, test continued OK, 5024 hrs+ has notreached F50 yet

EXAMPLE 17

Grafted HDPE bottle scrap from Example 4   50% (100 phr) Polyolefin(metallocene type) Affinity EG8200 (Dow)   7% (14 phr) HDPE HD6095(original bottle grade) 40.5% (81 phr) Catalyst masterbatch(added priorforming)  2.5% (5 phr) ESCR F50 553 hrs

EXAMPLE 18

Grafted HDPE bottle scrap from Example 4   50% (100 parts) HDPE GF 766047.5% (95 phr) Catalyst masterbatch  2.5% (5 phr) (added later, prior toforming) ESCR F20 at 3800 hrs, tested, has not reached F50 at 5335 hrs+

HDPE milk bottle scrap re-processed and not grafted or cross-linked,reached an ESCR of F50 at 3 hours only (i.e. failed) and as expectedalso failed the HST.

Original milk bottle grade polymer HD 6095 on injection moulded dumbell,tested under the same conditions reached an ESCR of F50 at 5 hours only.

There is very considerable and unexpectedly high improvements in theESCR after grafting and cross-linking.

1. A method of recycling and/or upgrading olefin (co)polymer scrapand/or mixtures of olefin (co)polymer scrap and an olefin (co)polymer,said method comprising adding effective amounts of a vinyl silane and afree radical initiator to graft the vinyl silane to the olefin(co)polymer.
 2. A method of upgrading olefin (co)polymer scrap and/ormixtures of olefin (co)polymer scrap and an olefin (co)polymer whichfails the ESCR test as defined in ASTM No. D1693B, said methodcomprising adding effective amounts of a vinyl silane and a free radicalinitiator to graft the vinyl silane to the olefin (co)polymer.
 3. Amethod according to claim 1, in which the olefin (co)polymer is anethylene (co)polymer.
 4. A method according to claim 3, in which theethylene (co)polymer is polyethylene, ethylene-propylene copolymer,ethylene-propylene-diene terpolymer (EPDM), ethylene vinyl acetatecopolymer (EVA) or copolymers of ethylene-alkyl acrylates.
 5. A methodaccording to claim 4, in which the polyethylene is high densitypolyethylene (HDPE), medium density polyethylene (MDPE), low densitypolyethylene (LDPE), very low density polyethylene (VLDPE), ultra lowdensity polyethylene (ULDPE) or linear low density polyethylene (LLDPE).6. A method according to claim 4, in which the copolymers ofethylene-alkyl acrylates are ethylene-ethyl acrylate (EEA),ethylene-butyl acrylate (EBA) and their terpolymers with maleicanhydride or mixtures thereof.
 7. A method according to claim 1, inwhich the olefin (co)polymers are metallocene catalyst (co)polymers. 8.A method according to claim 1, in which the (co)polymers have a specificgravity (S.G.) of above about 0.936.
 9. A method according to claim 8,in which the (co)polymer is HDPE.
 10. A method according to claim 9, inwhich the HDPE has a S.G. above about 0.942.
 11. A method according toclaim 10, in which the HDPE has a S.G. above about 0.945.
 12. A methodaccording to claim 10, in which the HDPE has a S.G. about 0.95 to about0.96.
 13. A method according to claim 1, in which the polymer is ahomopolymer.
 14. A method according to claim 1, in which the (co)polymeris collected, sorted, washed, granulated, pelletised, ground and/orfiltered prior to the grafting step.
 15. A method according to claim 14,in which the (co)polymer is dried prior to the grafting step.
 16. Amethod according to claim 15, in which the (co)polymer is dried tomoisture levels less than about 500 ppm.
 17. A method according to claim16, in which the (co)polymer is dried to moisture levels less than about200 ppm.
 18. A method according to claim 1, in which the vinyl silane isa vinyl alkoxy silane.
 19. A method according to claim 18, in which thevinyl alkoxy silane is vinyl-tris-methoxy-silane (VTMOS),vinyl-tris-methcxy-ethoxy-silane, vinyl-tris-ethoxy-silane,vinyl-methyl-dimethoxy-silane or gama-methacryl-oxypropyl-trismethoxy-silane.
 20. A method according to claim 19 in which the amountof vinyl silane and free radical initiator is about 0.5 to about 2.4% byweight of the (co)polymer.
 21. A method according to claim 20, in whichthe amount of vinyl silane and free radical initiator is about 0.8% toabout 2% by weight of the (co)polymer.
 22. A method according to claim18, in which the free radical initiator is a peroxide.
 23. A methodaccording to claim 22, in which the peroxide is dialkyl peroxide ordiaryl peroxide.
 24. A method according to claim 23, in which thedialkyl peroxide or diaryl peroxide is dicumyl peroxide (DCP, Dicup),di-tertiary-butyl peroxide (DTEP), di-tertiary-butyl-cumyl peroxide(DTBCP), di (tert-butylperoxy-isopropyl) benzene (Luperox F) or2,5-dimethyl-2,5-di (tert butylperoxy) hexane (Luperox 101).
 25. Amethod according to claim 23, in which the amount of the free radicalinitiator is about 0.05% to about 0.3% by weight of the (co)polymer. 26.A method according to claim 25, in which the amount of the free radicalinitiator is about 0.08% to about 0.2% by weight of the (co)polymer. 27.A method according to claim 26, in which the amount of the free radicalinitiator is about 0.10% to about 0.16% by weight of the (co)polymer.28. A method according to claim 1, in which the vinyl silane and freeradical initiator are pre-mixed and added to the (co)polymer in theirmixed form.
 29. A method according to claim 1, in which the ratio offree radical initiator to vinyl silane is about 1:10 to about 1:15. 30.A method according to claim 1, in which the grafting step is performedat a melt temperature of from about 180° C. to about 230° C.
 31. Amethod according to claim 30, in which the grafting step is performed ata melt temperature of from about 190° C. to about 220° C.
 32. A methodaccording to claim 31, in which the grafting step is performed at a melttemperature of from about 200° C. to about 220° C.
 33. A methodaccording to claim 1, in which one or more additives and/or fillersknown in the art of polymer processing are added either before, duringor after grafting of the vinyl silane.
 34. A method according to claim33, in which the additives are antioxidants, processing and/or thermalstabilisers, metal deactivators and/or copper inhibitors, UVstabilisers, blowing agents, catalysts, pigments, fillers and/or flameretardants.
 35. A method according to 34, in which the amount ofadditive is up to about 10% by weight based on the (co)polymer and theamount of filler is up to about 50% by weight of the (co)polymer.
 36. Amethod according to claim 1, in which either before, during or after thegrafting step, other (co)polymers, their scrap and/or mixtures thereofare added to enhance the properties of the recycled and/or upgraded (co)polymer.
 37. A method according to claim 36 in which the other(co)polymer is polyolefin, polypropylene, nitrile butadiene rubber,chlorinated polyethylene or chloro-sulfonated polyethylene.
 38. A methodaccording to claim 37, in which the polyolefin is ethylene vinyl acetatecopolymer (EVA), ethylene ethyl acrylate copolymer (EEA), ethylene butylacrylate copolymer (EBA), ethylene propylene rubber (EPR),ethylene-propylene copolymer (EPM), ethylene propylene-diene terpolymer(EPDM), ethylene-butylene copolymer (EBM), ethylene butylene-dieneterpolymer (EBDM), very low density polyethylene (VLDPE) ultra linearlow density polyethylene (ULDPE) linear low density polyethylene(LLDPE), low density polyethylene (LDPE) or medium density polyethylene(MDPE).
 39. A method according to claim 38, in which the other(co)polymer is added in an amount of from about 5% to about 50% byweight of the (co)polymer.
 40. A method according to claim 1, in whichthe recycled and/or upgraded (co)polymer is formed.
 41. A methodaccording to claim 40, in which the forming is conducted by injectionmoulding, blow moulding, compression moulding, extrusion calendering orconversion processes.
 42. A method according to claim 41, in which the(co)polymer is cross-linked.
 43. A method according to claim 42, inwhich the (co)polymer is cross-linked using a cross-linking catalyst.44. A method according to claim 43, in which the cross-linking catalystis added before, during or after the grafting step.
 45. A methodaccording to claim 42, in which the grafted and formed (co)polymercross-links naturally in the presence of humidity without a catalyst.46. A method according to claim 42, in which the grafted and formed(co)polymer is cross-linked in the presence of water, water vapour orsteam at temperatures from about ambient up to about 115° C.
 47. Olefin(co)polymer scrap and/or mixtures of olefin (co)polymer scrap and anolefin (co)polymer recycled and/or upgraded by the method defined inclaim
 1. 48. An article comprising at least a portion of the olefin(co)polymer scrap and/or mixtures of olefin (co)polymer scrap and anolefin (co)polymer according to claim
 47. 49. An article according toclaim 48, wherein the article comprises a bottle, container, box, tube,pipe, cable, profile, sheet, film or pre-form.
 50. A method according toclaim 20, in which the amount of vinyl silane and free radical initiatoris about 0.9% to about 1.4% by weight of the (co)polymer.
 51. A methodaccording to claim 36, in which the other (co)polymer is added in anamount of from 5 to about 95% by weight of the (co)polymer.
 52. A methodaccording to claim 1, wherein the olefin (co)polymer scrap and/ormixtures of olefin (co)polymer scrap and an olefin (co)polymer fails theESCR test as defined in ASTM No. D 1693B.
 53. A method of modifyingolefin polymer scrap and/or mixtures of olefin polymer scrap and anolefin polymer, said method comprising: providing olefin polymer scrapmaterial; providing an effective amount of a vinyl silane and a freeradical initiator; and reacting the components to graft the vinyl silaneto the olefin polymer to form a modified olefin polymer having vinylsilane grafted thereto.